The objectives of this project are: (1) To investigate the molecular biology of human cytomegalovirus (CMV) especially the viral gene functions and the virus, host cell interactions that might bear upon the mechanism of latency and the possible basis of herpesvirus oncogenesis. (2) To elucidate the route of virus transmission, and (3) to define the relationship between CMV strain variation and the protein or diverse clinical manifestations of CMV infection. The approaches to be used are based on our recent developmental work and can be categorized as follows: (a) Construction of a genetic and physical endonuclease fragment map of human CMV by restriction enzyme fragementation, gel electrophoresis, and nucleic acid hybridization techniques. (b) Studies of the mechanism of viral DNA replication by use of various inhibitors of macromolecular synthesis, restriction enzyme analysis, and electron microscopic analysis. (c) Studies of the regulation of gene expression in virus-infected permissive and non-permissive cells approached by various nucleic acid hybridization techniques and immunological analyses. (d) The classification of human cytomegalovirus strains by restriction enzyme DNA fragmentation, nucleic acid hybridization, protein SDS-gel electrophoresis, and immunological (antigenic) relatedness. (e) Observation of the relationship between virus strains and various clinical manifestations. (f) Localization of the viral genome and viral antigens in human tissue and determination of susceptible cell types and organs by in situ 3H cRNA-DNA cytohybridization and various immunofluorescence techniques in order to explore the natural state of human CMV, both latent and replicating, in man. These approaches should provide the necessary first steps for understanding the phenomena of latency, reactivation, and pathogenesis of human CMV, as well as its little-explored oncogenic potential.